1. Field of the Invention
The present invention relates to a constructional laser including a housing, a casing supported on the housing and having at least one beam hole, a motor-driven shaft supported in the housing for rotation about a rotational axis and having an end projecting into the casing, an arrangement for providing rotation-imparting connection between the shaft and the casing, a light source for emitting a laser beam and supported in the housing for rotation about the rotational axis, and a direction-changing device for the laser beam.
2. Description of the Prior Art
Constructional lasers with a rotatable laser beam, further just lasers, are used in the construction industry, in intallation, electrical and the like jobs as auxiliary means for laying down horizontal and vertical lines on ceilings, walls and floors or to exactly define horizontal and vertical planes in a certain area. This is particularly necessary for straightening of door cases and windows and for determining an exact horizontal course of conduits. The lasers are also used straightening of door cases and windows and for determining an exact horizontal course of conduits. The lasers are also used as auxiliary marking means for a horizontal and vertical alignment of attachment points.
The lasers of this type includes a laser light source which is arranged in the laser housing and the emitted laser beam of which is rotated about a rotational axis. The emitted laser beam is pivoted, at least partially, by 90.degree. with respect to the rotational axis by a direction-changing device and describes thus, during its rotation, a plane. The laser beam is aligned with respect to a constructional component with a leveling device, whereby an exact horizontal position and an exact vertical position of planes, which are defined by the rotatable laser beam, are insured. The leveling devices can be formed as manually adjustable devices. However, they can include an automatically adjustable servo component equipped with a servo-motor. To simplify the straightening of the laser beam or its rotational axis, display devices are provided on the laser housing which display a relative position of the rotational axis in the housing. The direction-changing device for pivoting or deflecting the laser beam, which is emitted by the laser light source, includes a mirror arrangement or a deviating prism, preferably, a pentaprism. The rotation of the laser beam is effected, e.g., by rotating the direction-changing device.
In one type of conventional lasers, the deflected laser beam exits through an arrangement of beam holes. The beam hole arrangement is so selected that they insure passing of the rotatable laser beam in all directions without any obstacles to a most possible extent. The beam holes should be formed of plane-parallel glass section having a high optical quality so that the passing laser beam is not deflected from the plane by refraction. The panes are usually formed as polygons and form a lantern-like member which is fixedly connected with the upper wall of the laser housing. The abutting edges of the panes are optically sealed to prevent damaging reflection. The sealing is preferably effected by stiffening of the lantern-like members. The stiffening should insure that the lantern-like member projects, without any damage, above the upper hall of the laser housing in case of its possible inclination. In view of the desired stiffness of the lantern-like member, a relatively large width of the lands is desirable in locations of the joints. On the other hand, the lands should not shade a too large region of the rotatable laser beam. The satisfaction of all of these contradictory requirements increases the manufacturing costs of the lantern-like pane members. In particular, the need in panes with a high optical quality for all of the beam holes and their exact arrangement substantially increases the manufacturing costs. The beam holes should be kept free from any soiling or dirt accumulation to prevent shading of the laser beam and to insure that soiling or dirt would not serve as scattering centers capable of deflecting the laser beam of a set plane. In addition, because of the required stiffness, the lantern-like pane members have a relatively large weight.
In another type of lasers with a rotatable laser beam, the direction-changing device is arranged in a rotatable casing projecting above the upper wall of the housing. The casing either partially or completely is arranged outside of the housing. A beam hole, which is formed in the side wall of the casing, provides for exit of the perpendicularly deflected laser beam component. For rotating the laser beam, the casing is rotated about its rotational axis. The transmission of a rotary movement to the casing is effected with motor-driven shaft axially extending in the laser housing, with the laser light source and other optical components being arranged inside the shaft which is made hollow. The shaft is connected with the casing by appropriate rotation-transmitting means. For purposes of economy of the power supply, which is usually provided by batteries, soft-running shaft bearings and a small-torque drive motor are used. This type of a laser, in comparison with a laser with lantern-like pane members, has a simpler construction and is cheaper in manufacturing. It has a separate, relatively small beam hole, which is closed with an optical glass and rotates together with the casing. The laser beam is not shaded by any stiffening. The possibly necessary cleaning of the beam hole can be effected relatively easy. However, this laser can be relatively easy damaged when subjected to mechanical loads. If the casing, which projects above the housing, is inclined, an impact applied to the casing is transmitted directly to the shaft. This may result in the damage of the soft running shaft bearings. With regard to the optical quality of the laser beam, a small beam cross-section requires relatively large distances. This requires the use of a precisely adjustable optical system. An impact can cause displacement of the optical components inside the shaft and distortion of their precise adjustment, which adversely affect the optical quality of the laser beam.
Accordingly, an object of the present invention is a constructional laser which is insensitive to mechanical loads to a most possible extent. Another object of the present invention is a constructional laser the beam optical quality of which is retained in case of inadvertent inclination of the apparatus. A further object of the present invention is a laser which is simple and cost-effective in manufacturing.